exists查询(query exists)

Mapper 内置方法

• exists(Where)：动态条件，exists查询

动态where查询

public class Demo {
    @Autowired
    private SysUserMapper sysUserMapper;
    
    public void exists() {
       boolean exists= sysUserMapper.exists(where->{
           where.like(SysUser::getUserName,"abc");
       });
    }
}

基于QueryChain(强大)

可构建复杂的场景, 更多操作前往 链路查询 - QueryChain ！

public class Demo {
    @Autowired
    private SysUserMapper sysUserMapper;

    public void count() {
        boolean exists= QueryChain.of(sysUserMapper)
                .like(SysUser::getUserName,"abc")
                .exists();
    }
}